CN110523426B - Preparation method of catalyst for glycerol oxidation - Google Patents
Preparation method of catalyst for glycerol oxidation Download PDFInfo
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Abstract
A method of preparing a catalyst for the catalytic oxidation of glycerol, comprising: mixing and stirring a solid alkali molecular sieve and a metal precursor solution to obtain a mixture 1; adding a sodium borohydride solution into the mixture 1 to perform a reduction reaction; and (3) carrying out solid-liquid separation after the reduction reaction, and drying the sorted solid 1 to obtain the catalyst for the catalytic oxidation of the glycerol. The Pt supported solid alkali mesoporous molecular sieve catalyst provided by the invention has the advantages that the carrier structure is very regular, the crystallinity is higher, and the alkaline earth metal oxide and Pt particles are uniformly dispersed on the surface of the catalyst, so that the catalytic activity is improved. The Pt supported solid base mesoporous molecular sieve catalyst prepared by the invention can be added with solid base to control the particle size and modulate the alkalinity of the molecular sieve on the premise of not damaging the carrier structure, and the catalytic performance of the catalyst is improved by utilizing the confinement effect of the mesoporous molecular sieve.
Description
Technical Field
The application belongs to the field of mesoporous molecular sieves, and relates to a preparation method of a glycerol oxidation catalyst, wherein the catalyst is a solid base mesoporous molecular sieve, in particular to a preparation method of a Pt supported solid base mesoporous molecular sieve catalyst.
Background
Alcohols are industrially important as a large class of organic substances as raw materials or intermediates. For example, a cheap glycerol raw material can be used for preparing a high value-added product glyceric acid through an oxidation reaction, the glycerol is an important byproduct in the process of preparing biodiesel, the molecule of the glycerol contains three functional groups, the glycerol has active chemical properties, and can participate in chemical reactions such as oxidation, polymerization and condensation, and meanwhile, the oxidation target product glyceric acid is used as an important medicine and a medicine intermediate, so that the glycerol has wide utilization value. Therefore, a reaction process for producing glyceric acid by oxidation of glycerin is attracting attention. It has been reported that the conversion rate of glycerol and the yield of glyceric acid can be improved by adding liquid alkali sodium hydroxide in the oxidation reaction of glycerol, but the obtained product is sodium glycerate, rather than the final product glyceric acid, which increases the difficulty of analysis and separation.
Chinese patent application publication No. 101279911A describes a method for preparing glyceric acid by catalytic oxidation of glycerol, wherein a functionalized carbon nanotube-supported metal catalyst is used. Chinese patent application publication No. 105688935A describes a catalyst Pt/Cu-Ni for alcohol catalytic oxidation.
The invention is especially provided for finding more and better alcohol catalytic oxidation catalysts, particularly for preparing glyceric acid by catalytic oxidation of glycerol and widening the application of glycerol oxidation.
Disclosure of Invention
It is an object of the present application to provide a process for the preparation of a catalyst for the catalytic oxidation of glycerol, which process produces a catalyst having an improved conversion of glycerol in the absence of a basic liquid.
Another objective of the present application is to provide a method for preparing a solid base mesoporous molecular sieve carrier by an in-situ synthesis method, which can not only retain the regular structure of the mesoporous carrier, but also make the surface of the mesoporous molecular sieve carrier have uniform alkaline site distribution.
Another objective of the present application is to provide a method for preparing a Pt-supported solid alkali mesoporous molecular sieve catalyst, in which the introduction of basic sites on the surface of the mesoporous molecular sieve can make the distribution of Pt particles more uniform, and the morphology of the Pt nanoparticles presents a unique "long strip" due to the confinement effect of the pore channels of the mesoporous molecular sieve.
In order to achieve the purpose, the following technical scheme is adopted in the application:
a method of preparing a catalyst for the catalytic oxidation of glycerol, comprising: mixing and stirring a solid alkali molecular sieve and a metal precursor solution to obtain a mixture 1; adding a sodium borohydride solution into the mixture 1 to perform reduction reaction; and (3) carrying out solid-liquid separation after the reduction reaction, and drying the sorted solid 1 to obtain the catalyst for the catalytic oxidation of the glycerol.
Wherein the solid alkali molecular sieve comprises MgO/SBA series solid alkali mesoporous molecular sieve, mgO/MCM series solid alkali mesoporous molecular sieve, mgO/KIT series solid alkali mesoporous molecular sieve and the like. Preferably, the solid alkali molecular sieve comprises a MgO/SBA series solid alkali mesoporous molecular sieve and a MgO/KIT series solid alkali mesoporous molecular sieve. More preferably, the solid base molecular sieve comprises a MgO/SBA-15 solid base mesoporous molecular sieve.
The catalyst-supported metal of the present application includes Pt.
The prepared catalyst is particularly suitable for the reaction for preparing glyceric acid by catalytic oxidation of glycerol, and improves the conversion rate of the glycerol and the selectivity of the glyceric acid.
The Pt supported solid base catalyst prepared by the method has the following bifunctional sites: the basic sites and metal sites form active sites on the surface of a neutral mesoporous molecular sieve (e.g., SBA-15). In particular, the SBA-15 mesoporous molecular sieve enables the platinum metal on the load to present a unique strip shape due to the limited domain effect of the mesoporous pore canal of the SBA-15, thereby being beneficial to the contact and mass transfer of reactants and products and enhancing the application of the catalyst in oxidation reaction.
Drawings
FIG. 1 is a high-power transmission electron microscope image of solid alkali molecular sieve MgO/SBA-15
FIG. 2Pt Supported solid base molecular Sieve catalyst (Mg/Si = 0.1)
FIG. 3 TEM image of Pt supported solid molecular sieve catalyst prepared according to one embodiment
FIG. 4 particle size distribution plot and TEM image of Pt supported solid molecular sieve catalyst prepared in certain embodiments
FIG. 5 is a graph of the reaction performance of catalysts prepared in certain embodiments
FIG. 6 XRD pattern of solid base molecular sieve support
Detailed Description
For better understanding of the inventive content of the present application, the technical solutions of the present application will be clearly and completely described below with reference to the specific embodiments, examples and drawings of the present application, and the following embodiments are used for illustrating the present application and are not intended to limit the scope of the present application.
Experimental procedures without specific conditions noted in the following examples, generally according to conventional conditions or according to conditions recommended by the manufacturers. All percentages, ratios, proportions, or parts are by weight unless otherwise specified.
The magnesium to silicon ratio in this application is the molar ratio of the elements.
The term "mesoporous" generally refers to a pore size of 2-50nm.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present application. The preferred embodiments and materials described herein are intended to be exemplary only. The term "TOF" is commonly used to measure the rate of catalytic reaction of a catalyst, the number of conversion of a single active site in a unit time, and the TOF value used to measure the catalytic activity of the catalyst is an important index in the present catalytic field
In certain embodiments herein, a method of preparing a Pt-supported solid base mesoporous molecular sieve catalyst comprises:
mixing a solid base SBA-15 molecular sieve with a Pt metal precursor solution, and stirring to obtain a mixture 1; adding a sodium borohydride solution into the mixture 1 to perform reduction reaction; and (3) carrying out solid-liquid separation after the reduction reaction, and drying the separated solid 1 to obtain the catalyst for the catalytic oxidation of the glycerol.
Wherein, the Pt metal precursor is selected from one or the mixture of more than two of chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate. Preferably, the Pt metal precursor is chloroplatinic acid.
The solid base mesoporous molecular sieve adopted in the application can be an MgO/SBA-15 molecular sieve prepared by taking magnesium salt as an alkali source, preferably, the solid base mesoporous molecular sieve adopts magnesium salt as the alkali source.
In certain embodiments, the Pt metal precursor solution is an aqueous chloroplatinic acid hexahydrate solution having a mass percent concentration of 0.02% to 0.05%; preferably 0.024% -0.04%.
In certain embodiments, the molar ratio of sodium borohydride to chloroplatinic acid hexahydrate added is from 20.
In the Pt-loaded MgO/SBA-15 solid alkali molecular sieve, an SBA-15 mesoporous molecular sieve is a highly ordered planar hexagonal phase and has a two-dimensional hexagonal pore passage, the pore size is 4.6-30 nm, the thickness of a silica pore wall is 3.1-6.0 nm, and the SBA-15 molecular sieve is a neutral material almost without any acidity or alkalinity. In the application, the alkaline site SBA-15 molecular sieve is introduced and then the Pt metal is loaded, so that the introduction of the alkaline site can play a role in concerted catalysis with the loaded Pt metal, the reaction activity of the catalyst is greatly improved, and particularly the conversion rate of glycerol is greatly improved for the selective oxidation reaction of the glycerol.
In the application, a chemical reduction method is adopted to load Pt metal on a solid alkali molecular sieve, sodium borohydride is adopted as a reducing agent, metal precursor molecules are diffused into a mesoporous channel in the stirring process of an added metal precursor solution and a carrier, and Pt nanoparticles can be rapidly reduced by adopting the sodium borohydride and limited to the mesoporous channel.
In certain embodiments, at the beginning of the dropwise addition of the sodium borohydride solution, 1/2 to 2/3 of the sodium borohydride solution is added at a dropwise rate ranging from 0.3mL/min to 0.7mL/min. Preferably, the first 1/2 sodium borohydride solution to begin the dropwise addition is added at 0.5mL/min to 0.65 mL/min.
In certain embodiments, the remaining sodium borohydride solution is added at a rate of between 1mL/min and 3 mL/min; preferably, the remaining sodium borohydride solution is added at a rate of from 1.5mL/min to 2mL/min. The remaining sodium borohydride solution may also be added dropwise at a rate below that which is preferred in order to compromise the overall time taken to prepare the catalyst.
In certain embodiments, the aqueous sodium borohydride solution is present in a concentration of 0.5% to 1.2% by weight, and preferably, in a concentration of 0.7% to 0.95% by weight.
In the metal reduction process, sodium borohydride is adopted to reduce metal precursor molecules, and metal is loaded on the mesoporous molecular sieve. Wherein, in order to ensure that the Pt metal is more uniformly distributed on the mesoporous molecular sieve and show better catalytic performance, the concentration of the sodium borohydride solution is preferably 0.5-1.2%, or the dropping speed of the sodium borohydride solution is controlled to be 0.3-0.7 mL/min. When the metal particle size is too large, the catalytic effect of the catalyst is poor, and when the reduction speed of sodium borohydride is too high, pt metal is gathered in the molecular sieve pore channel to cause the blockage of the mesopores. The reduction speed of sodium borohydride is determined by the concentration of the metal precursor and the dropping speed of sodium borohydride.
In certain embodiment embodiments, the mass percent concentration of the Pt metal precursor aqueous solution is controlled to be 0.02-0.05%; preferably from 0.024% to 0.04% sufficient to prevent agglomeration of the metal.
In the application, the particle size is better controlled by dripping the sodium borohydride solution by adopting a two-stage rate method, so that the Pt metal can be prevented from being aggregated on one hand, and the production efficiency can be improved on the other hand.
In certain embodiments, the loading of metallic Pt is controlled between 0.75 and 1.2 wt%. The loading capacity in the range has good effect on the glycerin oxidation catalytic reaction. The preferred control of loading around 1wt% works best.
When the metal precursor is chloroplatinic acid hexahydrate, the mass ratio of the solid base SBA-15 molecular sieve to the metal precursor is 1.
Controlling the drying temperature to be 25-80 ℃ in the drying process of the solid 1 obtained after reduction; preferably, solid 1 is dried under vacuum at a temperature of from 25 ℃ to 50 ℃.
The drying time of the solid 1 is determined according to actual conditions, and the moisture content of the solid can meet specific requirements. Preferably, the drying time is between 9 and 15 hours, more preferably between 10 and 12 hours.
The drying temperature should not exceed 80 deg.c to prevent oxidation of the Pt metal.
Specifically, the preparation method of the carrier solid base molecular sieve adopted by the application comprises the following steps:
(1) Adding a template agent P123 into an acid solution, and stirring until the template agent P123 is dissolved to obtain a solution 1;
(2) Adding an alkali source into the solution 1 and stirring to obtain a solution 2;
(3) And adding a silicon source into the solution 2, and stirring, crystallizing, rotary steaming and roasting to obtain the solid alkali SBA-15 molecular sieve.
The acid solution in the application comprises hydrochloric acid and/or sulfuric acid, preferably hydrochloric acid, and the concentration of the hydrochloric acid is controlled to be 1.4mol/L-2mol/L, and more preferably 1.6mol/L.
The alkali source in this application includes magnesium salts as the alkali source.
In certain embodiments, the magnesium salt of an alkaline source herein comprises one or a mixture of two or more of magnesium nitrate, magnesium chloride, and magnesium acetate, preferably magnesium acetate.
In the present application, the silicon source is one or a mixture of more than two of silica sol, water glass, solid silica gel, diatomite, silicate and tetraethyl orthosilicate, and tetraethyl orthosilicate is preferred.
The template P123 is a template commonly used for preparing SBA-15 and is named as a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer with the molecular weight of 5800.
The mass ratio of the template to the silicon source is 0.01.
In certain embodiments, the templating agent in step (1) is stirred for more than 6 hours, preferably 8 hours, to ensure that the templating agent has completely dissolved in the acidic solution.
In certain embodiments, the silicon source in step (3) may be added dropwise or may be poured rapidly, with rapid pouring being preferred in this application.
In the present application, the mass ratio of the alkali source to the silicon source is 0.01.
The alkali content of the basic sites plays an essential role for the metal loading and the redox reaction, wherein in the present application Mg/Si is between 0.05 and 0.3, preferably Mg/Si is between 0.05 and 0.2, more preferably Mg/Si is between 0.08 and 0.12.
In the method, when the Mg/Si ratio is 0.05-0.3, the metal load is uniformly dispersed on the mesoporous molecular sieve. The ratio of Mg/Si is 0.08-0.12, the Pt loaded particle size is the smallest, the distribution is the most uniform, and the glycerol oxidation effect is the best.
In some embodiments, the conditions during crystallization include: the crystallization temperature is 80-140 ℃, and the crystallization time is 12-60h; preferably, the crystallization temperature is 80-120 ℃, and the crystallization time is 12-48h; more preferably, the crystallization temperature is 100 ℃, and the crystallization time is 24h.
According to the method, the solid base SBA-15 molecular sieve prepared by crystallizing the mixed solution is most regular in internal pore channel arrangement, the pore channel is about 8nm, and the method is suitable for subsequent loading operation.
In certain embodiments, the post-treatment comprises rotary steaming, drying, and calcining.
In certain embodiments, the temperature during stirring in step (3) is between 35-45 ℃, preferably 40 ℃.
In certain embodiments, the method of low-temperature rotary evaporation can prevent the loss of the added alkali source on one hand, and particularly, the alkali source is magnesium salt, and the low-temperature rotary evaporation can uniformly distribute MgO at alkaline sites. Wherein the rotary evaporation temperature is 50-60 ℃.
Wherein the roasting effect is best at 550 ℃, and the template agent can be completely burnt out.
The invention also provides application of the Pt supported solid base mesoporous molecular sieve catalyst in glycerol oxidation reaction.
The Pt-loaded solid base mesoporous molecular sieve catalyst is applied to glycerol oxidation reaction to prepare glyceric acid, wherein the glycerol oxidation efficiency is improved by adding liquid base NaOH in the glycerol oxidation reaction, but the addition of the liquid base can cause that salt generated by a target product of the reaction is not beneficial to later purification and separation and does not conform to the idea of green chemistry.
Compared with the prior art, the method has the following beneficial effects:
the solid base mesoporous molecular sieve, especially the MgO/SBA-15 molecular sieve carrier, provided by the application has the advantages that the mesoporous pore canal distribution is very regular, the surface alkaline sites are uniformly distributed and do not generate an agglomeration phenomenon, the mesoporous pore canal is not blocked by MgO, the MgO is uniformly distributed on the surface and in the pore canal of the mesoporous SBA-15 molecular sieve, and the thermal stability of the SBA-15 molecular sieve in the application is good enough, so that the in-situ doped alkaline sites do not damage the mesoporous structure of the molecular sieve.
According to the method, the Pt nano metal is loaded into the solid alkali molecular sieve by adopting a sodium borohydride reduction method, a proper alkaline site is beneficial to the loading of the Pt nano metal, the loaded Pt metal has small particle size and is distributed uniformly, and the shape of the Pt metal presents a unique strip shape under the confinement effect of the mesopores of the solid alkali SBA-15 molecular sieve. The unique strip shape in the pore wall can ensure that glycerol molecules are diffused into the pore channel, and the glycerol molecules can be conveniently adsorbed and contacted with active sites under the condition of not influencing the mass transfer effect to be carried out in the conversion process of the glycerol molecules towards glyceric acid.
The Pt supported solid base mesoporous molecular sieve dual-function catalyst constructed by the application has the advantages that the proper alkaline sites are beneficial to the loading and dispersion of metal sites, the acting force of metal and a carrier is improved due to the addition of the alkaline sites, the leaching of Pt metal in the reaction process is prevented, and the stability of the catalyst is improved.
The Pt supported solid base mesoporous molecular sieve catalyst constructed by the application has a promising application space in the field of glycerol oxidation. No additional liquid base addition is required when using the catalyst of the present application and its reactivity has reached that of the liquid base addition. The catalyst can ensure that the conversion rate of the glycerol and the selectivity of glyceric acid are both as high as 60 percentThe TOF value can reach as high as 1500h -1 The above.
The following detailed description of the present invention is provided for the purpose of illustrating the embodiments of the present invention and is not intended to limit the scope of the invention.
The main analysis methods in the examples:
x-ray diffraction (XRD): x-ray powder diffractometer model X' Pert Pro MPD manufactured by Panalytical corporation of Pasacaceae, netherlands; transmission Electron Microscope (TEM): TEM sample analysis was performed by a transmission electron microscope of JEM-2100UHR type, JEOL, japan.
Example 1
(a) Synthesis of solid alkali molecular sieve carrier MgO/SBA-15
Dissolving 4g of P123 in 150ml of 1.6mol/L hydrochloric acid, stirring for 12h, adding 0.875g of magnesium acetate, continuously stirring for half an hour, quickly adding 8.5g of tetraethyl orthosilicate, stirring for 24h at 40 ℃, then placing the reaction solution in a 200ml crystal bloom kettle containing a polytetrafluoroethylene lining, placing the crystal bloom in a 100 ℃ drying oven for 24h, then carrying out rotary evaporation treatment on the solution after crystal bloom at 55 ℃ to evaporate the solution, drying at 100 ℃, roasting at 550 ℃ to obtain the MgO/SBA-15 molecular sieve carrier with the magnesium-silicon ratio of 0.1.
(b) Preparation of supported Pt metal catalyst
And (2) adding 1.2g of the prepared carrier in the step (a) and 0.036g of chloroplatinic acid hexahydrate into 150ml of deionized water, continuously stirring for half an hour, then weighing 0.09g of sodium borohydride, adding 100ml of water to prepare a sodium borohydride solution, adding the former half of the sodium borohydride solution dropwise at the speed of 0.55ml/min, adding the other half of the sodium borohydride at the speed of 2ml/min, stirring the reduced solution for 10 hours, performing suction filtration and washing on the solution, and performing vacuum drying at 25 ℃ to obtain the Pt-loaded MgO/SBA-15 solid alkali molecular sieve.
The morphology of the Pt supported MgO/SBA-15 solid base mesoporous molecular sieve obtained in the embodiment is detected by a transmission electron microscope.
It can be seen from fig. 1 that the pore and morphology of the in-situ synthesized molecular sieve are not damaged, the particle size of MgO is smaller and is distributed more uniformly, fig. 2 is a Pt-supported solid alkali molecular sieve catalyst, it can be seen from the figure that the metal-supported particle size is smaller, the particle size is uniformly distributed on the surface of the molecular sieve, and there is almost no agglomeration, and the Pt nano-metal is distributed in the pore of the mesopores due to the confinement effect, and presents a unique strip-shaped morphology.
The Pt supported solid base mesoporous molecular sieve catalyst in the application is represented by a Pt supported morphology shown in a transmission electron microscope in a figure 2, and can be understood as that metal Pt is uniformly supported on the pore wall along the length direction of the pore channel, and no agglomerated particles are formed in the pore channel.
Example 2
(a) Synthesizing a pure silicon type SBA-15 mesoporous molecular sieve:
dissolving 4g of P123 in 150ml of 1.6mol/L hydrochloric acid, stirring for 12h, then quickly adding 8.5g of tetraethyl orthosilicate, stirring for 12h at 40 ℃, then placing the reaction solution in a 200ml of crystal bloom kettle containing a polytetrafluoroethylene lining, placing the reaction solution in an oven for crystal bloom for 24h, then carrying out suction filtration and washing on the solution after crystal bloom, drying at 100 ℃, and roasting at 550 ℃ to obtain the pure silicon type SBA-15 molecular sieve carrier.
(b) The preparation of the supported Pt metal catalyst was the same as that used in experiment 1 (b).
Example 3
MgO is adopted as a molecular sieve carrier, wherein the MgO is adopted in the Shanghai test of China, and the CAS number is 1309-48-4. The loading method was also as shown in example 1 (b).
Example 4
In this example, the process and parameters of example 1 were adopted except that the dropping rate of the sodium borohydride solution was changed, and the dropping rate of the sodium borohydride solution was always 2ml/min.
When the Pt supported MgO/SBA-15 solid base mesoporous molecular sieve obtained in the embodiment is analyzed by a transmission electron microscope, as shown in FIG. 3, pt nanoparticles are aggregated seriously and are agglomerated to form large spherical particles.
Example 5
The difference from the example 1 lies in that the loading method in (b) is changed, and the specific implementation process is as follows by adopting an immersion method: 1g of the carrier of example 1 (a) 1.2g and prepared chloroplatinic acid solution (0.036 g/5 ml) were dipped in equal volume, and stood for 12h, then dried in a 100 ℃ oven, calcined in a muffle furnace at 450 ℃ for 3h, and then reduced with hydrogen at 400 ℃ for 4h to obtain the immersion Pt metal catalyst, which is marked as Pt/MgO/SBA-15 (IM)
As can be seen from fig. 4, the catalyst supported Pt prepared in this embodiment has a spherical morphology in the middle of the mesoporous channels, and the corresponding glycerol oxidation catalysis performance is inferior to that of the unique MgO/SBA-15 solid base molecular sieve supported with a strip morphology.
Example 6
The difference from the embodiment 1 is that (a) the prepared solid alkali molecular sieve only has rotary steaming and drying treatment and does not burn to remove the template agent, and (b) the loading method is consistent. The catalyst is marked as Pt/MgO/SBA-15 (UC)
As can be seen from fig. 4, due to the mesoporous blockage, the Pt nano-catalyst prepared in this embodiment only exists on the surface of the molecular sieve, and the glycerol oxidation catalytic performance corresponding to the partial agglomeration of the Pt metal is inferior to that of the MgO/SBA-15 solid alkali molecular sieve which presents a unique elongated shape and supports Pt.
Example 7
The solid base mesoporous molecular sieve adopted in the embodiment is MgO/SBA-15 solid base mesoporous molecular sieve, wherein the ratio of Mg/Si is 0.2.
Preparation of supported Pt metal catalyst
Adding 1.2g of MgO/SBA-15 solid base mesoporous molecular sieve (the Mg/Si ratio is 0.2) and 0.05g of chloroplatinic acid hexahydrate into 150ml of deionized water, continuously stirring for half an hour, then weighing 0.09g of sodium borohydride, adding the sodium borohydride into 100ml of water to prepare a sodium borohydride solution, adding the sodium borohydride solution dropwise in the first half at the speed of 0.07ml/min, adding the sodium borohydride in the other half at the speed of 2ml/min, stirring the reduced solution for 10 hours, performing suction filtration and washing on the solution, and performing vacuum drying at the temperature of 30 ℃ to obtain the Pt-loaded MgO/SBA-15 solid base molecular sieve.
Example 8
This example refers to example 1 for the process and process parameters for preparing Pt loaded MgO/SBA-15 solid base molecular sieve, which differs from example 1 in that 0.018g chloroplatinic acid is added in (b).
Example 9
This example refers to example 1, and the difference from example 1 is that (a) the solid base molecular sieve magnesium acetate is 0.4375g. Making Mg/Si =0.05.
Example 10
This example refers to example 1 for the process and process parameters for preparing Pt-loaded MgO/SBA-15 solid base molecular sieve, which is different from example 1 in that (a) solid base molecular sieve magnesium acetate is added in an amount of 0.7g, making Mg/Si =0.08.
Example 11
This example refers to example 1 for the process and process parameters for preparing Pt-loaded MgO/SBA-15 solid base molecular sieve, which is different from example 1 in that (a) solid base molecular sieve magnesium acetate is added in an amount of 1.75g, making Mg/Si =0.2.
Example 12
This example refers to example 1 for the process and process parameters for preparing Pt-loaded MgO/SBA-15 solid base molecular sieve, which differs from example 1 in that (a) solid base molecular sieve magnesium acetate is prepared in an amount of 2.1875g, making Mg/Si =0.25.
Example 13
(a) Synthesis of solid alkali molecular sieve carrier MgO/SBA-15
The process and parameters of the synthesis method of solid alkali molecular sieve carrier MgO/SBA-15 are as in example 1 (a), and the difference from example 1 (a) is that the amount of magnesium acetate added is different, and the Mg/Si =0.05 of the prepared solid alkali molecular sieve carrier MgO/SBA-15.
(b) Preparation of supported Pt metal catalyst
And (2) adding 1.2g of the prepared carrier in the step (a) and 0.040g of chloroplatinic acid hexahydrate into 150ml of deionized water, continuously stirring for half an hour, then weighing 0.07g of sodium borohydride, adding the sodium borohydride into 100ml of water to prepare a sodium borohydride solution, adding the sodium borohydride solution dropwise in the first half at a speed of 0.65ml/min, adding the sodium borohydride dropwise in the other half at a speed of 1.5ml/min, stirring the reduced solution for 10 hours, performing suction filtration and washing on the solution, and performing vacuum drying at 25 ℃ to obtain the Pt-loaded MgO/SBA-15 solid alkali molecular sieve.
Example 14
(a) Synthesis of solid alkali molecular sieve carrier MgO/SBA-15
The process and parameters of the synthesis method of solid alkali molecular sieve carrier MgO/SBA-15 are as in example 1 (a), and the difference from example 1 (a) is that the amount of magnesium acetate added is different, and the Mg/Si =0.08 of the prepared solid alkali molecular sieve carrier MgO/SBA-15.
(b) Preparation of supported Pt metal catalyst
And (2) adding 1.2g of the prepared carrier in the step (a) and 0.048g of chloroplatinic acid hexahydrate into 150ml of deionized water, continuously stirring for half an hour, then weighing 0.12g of sodium borohydride, adding the sodium borohydride into 100ml of water to prepare a sodium borohydride solution, adding the first half of the sodium borohydride solution dropwise at the speed of 0.7ml/min, adding the other half of the sodium borohydride at the speed of 2ml/min, stirring the reduced solution for 10 hours, carrying out suction filtration and washing on the solution, and drying the solution in vacuum at the temperature of 25 ℃ to obtain the Pt-loaded MgO/SBA-15 solid alkali molecular sieve.
Example 15
(a) Synthesis of solid alkali molecular sieve carrier MgO/SBA-15
The process and parameters of the synthesis method of solid basic molecular sieve carrier MgO/SBA-15 are as in example 1 (a), except that the amount of magnesium acetate added is different from that of example 1 (a), and the Mg/Si =0.2 of the prepared solid basic molecular sieve carrier MgO/SBA-15.
(b) Preparation of supported Pt metal catalyst
And (2) adding 1.2g of the prepared carrier in the step (a) and 0.036g of chloroplatinic acid hexahydrate into 150ml of deionized water, continuously stirring for half an hour, then weighing 0.09g of sodium borohydride, adding 100ml of water to prepare a sodium borohydride solution, adding the former half of the sodium borohydride solution dropwise at the speed of 0.50ml/min, adding the other half of the sodium borohydride at the speed of 3ml/min, stirring the reduced solution for 10 hours, performing suction filtration and washing on the solution, and performing vacuum drying at 25 ℃ to obtain the Pt-loaded MgO/SBA-15 solid alkali molecular sieve.
Example 16
(a) Synthesis of solid alkali molecular sieve carrier MgO/SBA-15
The process and parameters of the synthesis method of solid basic molecular sieve carrier MgO/SBA-15 are as in example 1 (a), except that the amount of magnesium acetate added is different from example 1 (a), and the Mg/Si =0.25 of the prepared solid basic molecular sieve carrier MgO/SBA-15.
(b) Preparation of supported Pt Metal catalyst
And (2) adding 1.2g of the prepared carrier in the step (a) and 0.039g of chloroplatinic acid hexahydrate into 150ml of deionized water, continuously stirring for half an hour, then weighing 0.09g of sodium borohydride, adding 100ml of water to prepare a sodium borohydride solution, adding the first half of the sodium borohydride solution dropwise at the speed of 0.55ml/min, adding the other half of the sodium borohydride at the speed of 1.5ml/min, stirring the reduced solution for 9 hours, carrying out suction filtration and washing on the solution, and drying at 50 ℃ to obtain the Pt-loaded MgO/SBA-15 solid alkali molecular sieve.
As shown in fig. 6, which is an XRD diffractogram, small-angle XRD peaks of the solid alkali molecular sieve MgO/SBA-15 carrier prepared in step (a) of examples 1-3,9-12 are all intact, which indicates that, within the scope of the present application, the solid alkali molecular sieve still maintains the intact channel structure because the addition of in-situ MgO cannot destroy the inherent structure of the molecular sieve, and that the solid alkali molecular sieve in wide-angle XRD has no characteristic MgO peak, indicating that the in-situ doped MgO is well dispersed and no agglomeration occurs.
Experimental example 1
In this experiment, the Pt-loaded MgO/SBA-15 solid base molecular sieve, pt/SBA-15 and Pt/MgO catalysts prepared in examples 1-3 and 9-12 of the present invention were applied to the glycerol oxidation reaction, and the specific experimental scheme was as follows: weighing 0.2g of the loaded Pt metal catalyst and a prepared raw material glycerol aqueous solution (0.5 g/25 ml), adding the Pt metal catalyst and the prepared raw material glycerol aqueous solution into a reaction kettle, wherein the pressure of oxygen for reaction is 1Mpa, the reaction temperature is 60 ℃, when the reaction temperature reaches 60 ℃, opening an oxygen valve to ensure that the oxygen of 1Mpa is filled into the reaction kettle, starting stirring and timing, stopping the reaction after the reaction is carried out for 8 hours, taking the reaction solution into a centrifuge tube, centrifuging, taking clear liquid for subsequent chromatographic analysis, and obtaining the result shown in Table 1
TABLE 1 catalyst Glycerol Oxidation Experimental results
The experimental results in Table 1 show that the effect of the solid base catalyst is obviously better than that of Pt/SBA-15 and Pt/MgO catalysts, the oxidation performance of the Pt/SBA-15 catalyst is weaker because the surface of the Pt/SBA-15 catalyst only has metal sites, and the products such as glyceric acid and the like are over oxidized because the Pt/MgO catalyst shows too strong alkaline sites.
In addition, the catalytic performance of the Pt-supported solid alkali molecular sieve catalysts prepared in example 1 (Pt/MgO/SBA-15 (0.1)), example 2 (Pt/SBA-15), example 5 (Pt/MgO/SBA-15 (IM)), and example 6 (Pt/MgO/SBA-15 (UC)) in glycerol oxidation was examined according to the method of this experimental example, and the results are shown in fig. 5, and the catalytic performance of the Pt-supported solid alkali molecular sieve MgO/SBA-15 catalyst prepared by the sodium borohydride reduction method in this application is better.
The present application is described in detail for the purpose of enabling those skilled in the art to understand the content of the present application and to implement the same, and the scope of the present application should not be limited thereby.
Claims (19)
1. The application of a catalyst in the catalytic oxidation of glycerol, wherein the preparation method of the catalyst comprises the following steps: mixing and stirring a MgO/SBA-15 solid alkali molecular sieve and a Pt metal precursor solution to obtain a mixture 1, wherein the mass ratio of Mg/Si in the MgO/SBA-15 solid alkali molecular sieve is 0.05-0.3;
adding a sodium borohydride solution into the mixture 1 to perform reduction reaction;
after the reduction reaction, carrying out solid-liquid separation, and drying the sorted solid 1 to obtain the catalyst for the catalytic oxidation of the glycerol; wherein the content of the first and second substances,
the preparation method of the MgO/SBA-15 solid alkali molecular sieve comprises the following steps:
(1) Adding a template agent P123 into an acid solution, and stirring until the template agent P123 is dissolved to obtain a solution 1;
(2) Adding magnesium salt into the solution 1 and stirring to obtain a solution 2;
(3) Adding a silicon source into the solution 2, wherein the mass ratio of the template agent P123 to the silicon source is 0.01-0.03.
2. The use of claim 1, wherein the Pt metal precursor comprises one or a mixture of more than two of chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate.
3. The use according to claim 2, wherein the molar ratio of sodium borohydride to chloroplatinic acid added is from 20 to 1 to 50.
4. Use according to any of claims 1-3, characterized in that the loading of the metal is controlled between 0.75-1.2 wt%.
5. The use according to any one of claims 1 to 3, wherein, at the beginning of the dropwise addition of the sodium borohydride solution, a volume of the sodium borohydride solution of 1/2 to 2/3 is added at a rate of the dropwise addition of 0.3mL/min to 0.7mL/min.
6. The use according to claim 5, wherein the remaining sodium borohydride solution is added at a rate of from 1mL/min to 3 mL/min.
7. Use according to any one of claims 1 to 3, characterized in that the mass concentration for the sodium borohydride solution is between 0.5% and 1.2%.
8. Use according to any one of claims 1 to 3, characterized in that the mass ratio of Mg/Si in the MgO/SBA-15 solid base molecular sieve is between 0.05 and 0.2.
9. The use according to claim 2, wherein the Pt metal precursor solution is present at a concentration of 0.02 to 0.05% by mass.
10. The use according to claim 2, wherein the Pt metal precursor solution is present at a concentration of 0.024% to 0.04% by mass.
11. The use according to claim 2, wherein the molar ratio of sodium borohydride to chloroplatinic acid added is from 30 to 1.
12. The use according to any one of claims 1 to 3, wherein when the Pt metal precursor is chloroplatinic acid hexahydrate, the mass ratio of the solid base SBA-15 molecular sieve to the Pt metal precursor is from 1.03 to 1.
13. The use according to any one of claims 1 to 3, wherein when the Pt metal precursor is chloroplatinic acid hexahydrate, the mass ratio of the solid base SBA-15 molecular sieve to the Pt metal precursor is 1.
14. The use according to claim 5, wherein the remaining sodium borohydride solution is added at a rate of from 1.5mL/min to 2mL/min.
15. Use according to any one of claims 1 to 3, characterized in that the mass concentration for the sodium borohydride solution is between 0.7% and 0.95%.
16. Use according to any one of claims 1 to 3, characterized in that the mass ratio of Mg/Si in the MgO/SBA-15 solid base molecular sieve is between 0.08 and 0.12.
17. The use according to claim 1, wherein the mass ratio of the templating agent P123 to the silicon source is 0.015.
18. The use according to claim 1, wherein the mass ratio of magnesium salt to silicon source is 0.01.
19. Use according to claim 1, characterized in that the mass ratio of magnesium salt to silicon source is 0.05.
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